import java.util.BitSet;

//Generates a crc32 checksum for a given string or byte array
public class crc32 {
    
    public static void main(String[] args) {
        System.out.println(Integer.toHexString(crc32("Hello World")));
    }
    
    public static int crc32(String str) {
        return crc32(str.getBytes());
    }
    
    public static int crc32(byte[] data) {
        BitSet bitSet = BitSet.valueOf(data);
        int crc32 = 0xFFFFFFFF;                           //initial value
        for(int i=0;i<data.length*8;i++) {
            if(((crc32>>>31)&1) != (bitSet.get(i)?1:0))
                crc32 = (crc32 << 1) ^ 0x04C11DB7;        //xoring with polynomial
            else
                crc32 = (crc32 << 1);
        }
        crc32 = Integer.reverse(crc32);                   //result reflect
        return crc32 ^ 0xFFFFFFFF;                        //final xor value
    }

}
